1.       下载log4j解压后在目录jakarta-log4j-1.2.8\dist\lib找到log4j-1.2.8.jar文件拷到

<Catalina-home>/webapps/test/WEB-INF/lib目录下

2.       创建log4j的配置文件log4j.properties,存于目录：

<Catalina-home>/webapps/test/WEB-INF

       文件内容：

       log4j.rootLogger=DEBUG, consoleLogger, fileLogger

log4j.appender.consoleLogger=org.apache.log4j.ConsoleAppender

log4j.appender.consoleLogger.layout=org.apache.log4j.PatternLayout

log4j.appender.consoleLogger.Threshold=DEBUG

log4j.appender.consoleLogger.layout.ConversionPattern=%c{2} - %m%n

log4j.appender.fileLogger=org.apache.log4j.RollingFileAppender

log4j.appender.fileLogger.File=c:/tomcat/webapps/test/WEB-INF/blog.txt

log4j.appender.fileLogger.MaxFileSize=1000KB

# 保留5个旧的日志文件

log4j.appender.fileLogger.MaxBackupIndex=5

log4j.appender.fileLogger.layout=org.apache.log4j.PatternLayout

# 日志格式：按照WebSphere通用日志格式相似的方式记录

log4j.appender.fileLogger.layout.ConversionPattern=[%d] %t %c %-5p - %m%n

3.       创建Blog4jServlet.java：

import org.apache.log4j.Logger;

import org.apache.log4j.PropertyConfigurator;

public class BLog4jServlet extends HttpServlet {

public void init(ServletConfig config) throws ServletException {       

        try{

            String path = config.getServletContext().getRealPath("/");

            String propfile = path + config.getInitParameter("propfile");

            PropertyConfigurator.configure(propfile);

        }catch(Exception e){

            System.out.println(e.getMessage());

        }

        }

}

4.     修改web.xml，加入如下代码：

<servlet>

     <servlet-name>log4j</servlet-name>

<servlet-class>binclude.BLog4jServlet</servlet-class>

<init-param>

<param-name>propfile</param-name>

<param-value>/WEB-INF/log4j.properties</param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

5.     在需要调用log的时候：

import org.apache.log4j.*;

static Logger logger = Logger.getLogger(DispatchServlet.class.getName());

logger.debug("this is a log message from" + logger.getName());

logger.info("info from" + logger.getName());

logger.warn("warn " + logger.getName());

logger.error("error" + logger.getName());